Foodborne botulism is a serious condition in which the patient experiences a gradual flaccid paralysis, 18 to 36 hours following consumption of contaminated food. If untreated, botulism can be fatal. Treatment is a lengthy process that may require hospitalization for several months with continuous mechanical ventilation (CDC, 1998, Dembek et al, 2007).
Botulinum neurotoxins (BoNTs) are the causative agents of botulism, and are the most potent naturally-occurring toxins known (Lamanna, 1959). There are seven serotypes of BoNTs, designated A through G, with serotypes A, B, E and F most frequently associated with human cases of botulism (Hatheway, 1990). BoNT/A is the most widely studied and best characterized of the BoNT serotypes—a cursory survey of the scientific literature indicates that there are approximately three times as many publications about BoNT/A than the next most frequent serotype, BoNT/B.
In the United States from 2001 to 2007, a total of 139 cases of foodborne botulism were reported to the Centers for Disease Control and Prevention (CDC). The majority of these cases were caused by intoxication by BoNT/A (76 cases) or BoNT/E (46 cases), with only 10 cases directly linked to consumption of food contaminated with BoNT/B. However, in the same seven years, BoNT/B was the causative agent of 387 of the 663 cases of infant botulism (58.4%) recorded by the CDC (National Botulism Surveillance, 2001-2007).
Although BoNT/B is a less frequently observed cause of foodborne botulism, it is nonetheless a significant threat to food safety. The largest recorded outbreaks of foodborne botulism to occur in both the United States and United Kingdom (UK) were attributed to the consumption of food contaminated with BoNT/B. In April 1977 in Michigan, a total of 59 patients were diagnosed with type B botulism, caused by eating a sauce made from improperly home-canned jalapenos. Eleven of the patients required hospitalization, although there were no reported deaths (Terranova et al., 1978). In June 1989 in the UK, 27 patients were intoxicated (one of whom died) by BoNT/B-contaminated hazelnut yoghurt (O'Mahony et al., 1990).
At the molecular level, BoNT/A and BoNT/B function in a similar manner. Both toxins are comprised of a 100 kDa heavy chain (Hc) and a 50 kDa light chain (Lc), linked by a single disulphide bond. The Hc functions by binding nerve cells and facilitates the internalization of the Lc, a zinc metalloprotease, into the pre-synaptic neuron at the neuromuscular junction (Montecucco & Schiavo, 1994; Simpson 2004). The Lc of BoNT/A cleaves synaptosomal-associated protein 25 (SNAP-25) whereas the Lc of BoNT/B cleaves synaptobrevin-2 (Schiavo et al., 1992; Blasi et al., 1993). Either cleavage event prevents the docking of acetylcholine-carrying vesicles with the presynaptic membrane, thus blocking the release of the neurotransmitter into the neuromuscular junction and ultimately prohibiting the contraction of the muscle (Simpson, 2004).
The development of a sensitive sandwich ELISA for the detection of BoNT/A, with a detection limit of 2 pg/mL was recently reported (Stanker et al., 2008). The mAbs (F1-2, F1-5 and F1-40) that form the foundation of this sandwich ELISA have been extensively characterized. Binding of these antibodies to the other serotypes of BoNT was undetectable (Stanker et al., 2008; Scotcher et al., 2009a & b). Whilst these studies have allowed the development of a test specific for BoNT/A, it is now necessary to develop a novel collection of mAbs to facilitate the development of a sandwich ELISA-based test specific to BoNT/B.